/*
 *  Copyright 2008-2010 NVIDIA Corporation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#pragma once

namespace thrust {

namespace random {

namespace detail {

template < typename T, T a, T c, T m, bool = (m == 0) >
struct static_mod {
    static const T q = m / a;
    static const T r = m % a;

    __host__ __device__
    T operator()(T x) const {
        if (a == 1) {
            x %= m;
        } else {
            T t1 = a * (x % q);
            T t2 = r * (x / q);
            if (t1 >= t2) {
                x = t1 - t2;
            } else {
                x = m - t2 + t1;
            }
        }

        if (c != 0) {
            const T d = m - x;
            if (d > c) {
                x += c;
            } else {
                x = c - d;
            }
        }

        return x;
    }
}; // end static_mod


// Rely on machine overflow handling
template<typename T, T a, T c, T m>
struct static_mod<T, a, c, m, true> {
    __host__ __device__
    T operator()(T x) const {
        return a * x + c;
    }
}; // end static_mod

template<typename T, T a, T c, T m>
__host__ __device__
T mod(T x) {
    static_mod<T, a, c, m> f;
    return f(x);
}; // end static_mod

} // end detail

} // end random

} // end thrust

